The present invention is directed to a standup screwgun. More particularly, the present invention is directed to standup screwguns capable of driving fasteners in excess of six inches in length.
The problem with driving such long fasteners is maintaining the overall tool length a managable length. One solution to this problem and a discussion of the parameters appear in U.S. Pat. No. 4,236,555, the relevant portions of which are hereby incorporated by reference. The solution disclosed therein was to collapse the screw feed attachment from both ends; that is, to collapse the nosepiece along with the fastener back toward the drive bit as well as collapsing the bit-containing end forwardly during screw feeding and driving.
This solution has been successful in maintaining a reasonable overall tool length for fasteners up to eight inches in length. The building industry in general and, more particularly, the built up roofing segment of the industry, is demanding ten and twelve inch fasteners and drive tools therefor to attach the thicker insulative boards to the roof decks. Double collapsibility alone, is insufficent to maintain reasonable tool lengths for these fastener lengths.
The present invention enables a reasonable length tool to be developed for feeding twelve inch fasteners. In order to accomplish this, it was necessary to identify a section of the tool capable of being shortened and providing the structure to make it possible. The shortenable section is the region where the fastener is transferred from the feed tube to the guide tube. By decreasing the angle between the two tubes, the length of the interface between them is increased. Two triangular panel members have one side generally coextensive with the inner surface of each tube and a third side forming a camming surface for laterally deflecting the head from the feed tube into the guide tube. This structure permits the leading end to transfer more gradually while the head is moved laterally very quickly reducing the length of this region to only a few inches.
A further feature of the present invention is the provision of means to prevent insertion of an inverted fastener into the guide tube. In field applications, a workman generally reaches into a pouch, grabs one of these long fasteners somewhere between its ends, extracts it and inserts it into the feed tube. If the workman is not paying close attention he may inadvertently insert the headed end first. Collapsing of the driver bit toward the pointed fastener end can result in a jammed or broken bit and possibly cause other damage to the tool.
The misfeed prevention feature of this invention is, then, important to overall tool life and operation. This feature comprises first and second offset feed tubes with a sloping interconnecting transition section. The height of the first tube and amount of incline of the transition section are such, for a particular minimum length and head diameter fastener, that entry into the second feed tube by an improperly oriented fastener is prevented. The misfeed prevention feature can be performed by the camming surface or by a specially configured funnel.
Other features, characteristics and advantages of the present invention will be more fully understood after a reading of the following specification when taken in conjunction with the accompanying drawings.